The Chancellor had suggested that Scotland could be forced to join the struggling European single currency if it votes for independence.

Mr Salmond later appeared to extend an olive branch to Mr Cameron and Mr Clegg, when he invited them for talks to discuss a way forward “in Edinburgh, in London or wherever”.

However, a Downing Street spokesman rejected the idea that Mr Cameron would be summoned for talks with the Scottish leader.

“We expect Alex Salmond to speak to the Scottish Secretary in the first instance,” he said.

Sources close to the Prime Minister said Mr Salmond “could not have it both ways”.

“He’s complaining about our interference and then asking for more involvement,” the source said. “It doesn’t work like that.”

Mr Cameron this week forced the issue of independence by insisting Holyrood did not have the power to call a legally-binding referendum without his permission. The Government is now taking legal advice on lending him the power to hold a vote.

However, senior Liberal Democrats and Labour politicians are concerned that Mr Cameron's tactics may be playing into the hands of nationalists.

Lord Ashdown, the former Liberal Democrat leader, claimed the Prime Minister has already "bungled" his handling of Scotland's vote on independence and should resign if the union breaks up.

The senior parliamentarian said Mr Cameron's position would be untenable if Scotland votes to become an independent nation.

He described Mr Cameron and Mr Salmond as "two high-pressure egos" engaged in a fight for their survival as leaders.

“What worries me is that this debate has got off at a very bad pace," Lord Ashdown told the BBC. "You have two high-pressure egos who are fighting each other on the TV screens.

"This is high noon. Only one of these two men is going to be standing at the end. Mr Cameron cannot continue as PM of Great Britain if he loses and Mr Salmond cannot continue as prime minister of Scotland.”

On the timing of a referendum, Lord Ashdown said there had been “a rather bungled launch of this by the Prime Minister and George Osborne”.

The Prime Minister's official spokesman dismissed the suggestion that he could eventually be forced to resign over the issue.